1. Field of the Invention
The present invention is generally concerned with wiring accessories adapted to fit over the previously bared end of the conductive core of an insulated electric conductor in order to facilitate and render more secure the connection to a terminal of any kind, especially when the conductive core comprises multiple strands.
It is more particularly directed to wiring accessories usually referred to as electric terminal connectors comprising a generally tubular metal part adapted to fit over the previously bared end of the conductive core of the insulated electric conductor concerned and an insulative sleeve having a front portion engaged with the metal part and a rear portion larger than the front portion adapted to fit over the corresponding end of the insulation of the electric conductor.
2. Description of the Prior Art
One of the problems to be overcome in the manufacture of electric terminal connectors of this kind concerns the fastening together of the metal part and the insulative sleeve.
At present this is usually done by overmolding.
This is the case, for example, with the electric terminal connector which the subject matter of French patent 1 468 859 and published French patent application 2 277 419.
For anchoring it into the insulative sleeve the metal part has at the inner end a frustoconcial enlargement with both sides of which the synthetic material constituting the insulative sleeve is in contact.
Although this arrangement has proved satisfactory and may continue to prove satisfactory it has the following disadvantages.
Firstly, and most importantly, it is difficult to place the metal part in the mold for overmolding the insulative sleeve, which is detrimental to productivity and therefore to manufacturing cost.
In an electric terminal connector with the insulative sleeve overmolded in this way onto the metal part, if the molding interface between the insulative sleeve and the metal part is not properly controlled (and this is not necessarily a simple matter), the molding interface can constitute an obstacle to some strands of the conductive core to be inserted into the metal part and so block the strand or strands concerned. This represents an impediment to correct placing of the electric terminal connector currently being fitted, which may lead to its rejection, and (if the electric terminal connector is eventually fitted despite this difficulty) can lead to problems at a later stage, for example if the strands that were blocked project from the electric terminal connector or are broken off and escape from it. This is quite independent of the effect of any such blocking of strands on the electrical quality of the connection that results.
It has also been proposed to join the insulative part and the metal part of an electric terminal connector together by crimping.
This is the case, for example, in published French patent application 2 579 836 which is specifically concerned with an electric terminal connector and in U.S. Pat. No. 2,964,171, which is more specifically concerned with an eyelet-type wiring tag.
Following its insertion into the previously formed insulative part, the inner end of the metal part is deformed within the latter by expanding it so that its shape then matches the corresponding portion of the insulative part.
However, the corresponding deformation is limited to placing the inner end of the metal part worked on in this way against the relevant wall of the insulative part.
To facilitate such deformation the metal part is usually divided into separate tangs, as is the case in the aforementioned published French patent application.
The risks of blocking some strands briefly outlined hereinabove for assembly by overmolding are encountered in a similar way and even in an accentuated way with such assembly by crimping.
This effect is even more marked given that, as shown by experience, there occurs at the end of such crimping and by virtue of its inherent elasticity some degree of "rebound" of the previously crimped portion of the metal part relative to the insulative part, especially where, as mentioned above, the metal part is to this end divided into separate tangs, the more massive insulative part being relatively rigid in comparison with such tangs.
This "rebound" of the crimped portion of the metal part causes the latter in practise to project into the internal space of the insulative part, with the attendant risk of blocking some strands, which is best avoided.
Furthermore, the crimping force that has to be applied is relatively high, for example in the order of 35 kg for an electric terminal connector in which the metal part has a cross-section of 1.5 mm.sup.2. In practise it is necessary to provide a backing member externally of the insulative part to absorb this force, which complicates the operation and is detrimental to the overall cost. It also further accentuates the stiffness of the insulative part relative to the metal part, accentuating the "rebound" which is best avoided.
A general object of the present invention is an arrangement for carrying out (or contributing to the carrying out of) the assembly of the insulative and metal parts of an electric terminal connector in a simple and effective way and without any resulting risk of blocking some strands.